Biofuel having improved cold flow properties

ABSTRACT

A biodiesel may be prepared using an admixture of petroleum diesel and an algal derived hydrotreated renewable diesel which can be treated with petroleum diesel cold flow additives. The resulting diesel fuel may be employed even in cold climates despite the high paraffin content and high degree of saturation of the hydrotreated renewable diesel component of the fuel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Ser. No. 61/599,628 filed on Feb. 16, 2012, the entire disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE DISCLOSURE

1. Field of the Invention

The present invention relates to hydrotreated renewable diesel fuels. The present invention particularly relates to renewable diesel fuels including hydrocarbons derived from algae.

2. Background of the Prior Art

As the cost of crude oil increases, numerous efforts have been made to find and develop alternative fuels, particularly fuels that are renewable, rather than those having a fossil source. Considerable effort has been expended researching potential fuels from regenerable biological sources, or biofuels. Conventional biodiesel is a diesel fuel-equivalent, processed fuel derived from biological sources (such as vegetable oil and animal tallow), which may be used in unmodified diesel engine vehicles.

Algae have gained a significant importance in recent years given their ability to produce lipids, which can be used to produce sustainable biofuel. Algae's superiority as a biofuel feedstock arises from a variety of factors, including high per-acre productivity compared to typical terrestrial oil crop plants, non-food based feedstock resources, use of otherwise non-productive, non-arable land, utilization of a wide variety of water sources (fresh, brackish, saline, and wastewater), production of both biofuels and valuable co-products such as carotenoids and chlorophyll.

The processing of biofuels is not without problems. For example, many biofuels are higher in viscosity and/or have cold flow temperatures that are too high for use in non-tropical applications. It may be desirable in the art of preparing biofuels using algae to reduce the cold flow temperatures of same.

SUMMARY OF THE INVENTION

In one aspect, the invention is a biofuel comprising hydrotreated renewable diesel, and at least one petroleum diesel cold flow improver.

In one aspect, the invention is a biofuel comprising an admixture of petroleum diesel, hydrotreated renewable diesel, and at least one petroleum diesel cold flow improver.

In another aspect, the invention is a biofuel comprising an admixture of petroleum diesel, hydrotreated renewable diesel, and at least one petroleum diesel cold flow improver, and further comprising a synergist.

In still another aspect, the invention is a method of preparing a biofuel comprising an admixture of petroleum diesel, hydrotreated renewable diesel, and at least one petroleum diesel cold flow improver wherein the at least one petroleum diesel cold flow improver is introduced into an admixture of petroleum diesel, hydrotreated renewable diesel at a temperature above the cloud point of the admixture of petroleum diesel, hydrotreated renewable diesel.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the invention is a biofuel comprising an admixture of petroleum diesel, a hydrotreated renewable diesel, and at least one petroleum diesel cold flow improver. For the purposes of this application, the term “hydrotreated renewable diesel,” which is sometimes abbreviated “HTRD,” is a hydrocarbon produced from vegetable oil, animal fat or, most preferably, algae which has been subjected to hydrogenation. The hydrogenation, also sometimes referred to as hydrotreating, is a process wherein hydrogen radicals are introduced into a hydrocarbon thereby saturating most or all unsaturated bonds. In some instances, this process may also reduce nitrogen and sulfur levels as well, particularly in the case of petroleum derived hydrocarbons. Usually hydrotreating is performed using a catalyst, but for the purposes of this application, the hydrogenation may be employed using any method known to be useful to those of ordinary skill in the art.

The HTRD used with the embodiments of this application may be essentially completely saturated and have a very narrow paraffin distribution. For the purposes of this application, the term paraffin distribution refers to the similarity of paraffin components. The similarity of the paraffin components can be illustrated by boiling point ranges or carbon number ranges. For example, a broad distribution would be one where the carbon number and/or boiling point of the paraffins in a diesel are substantially different. One example of a comparatively broad distribution would be one where the paraffinic compounds present in a diesel had a carbon number range of from about 8 to about 22. In contrast, a narrow distribution may be from about 15 to about 19.

Because HTRD is high in paraffinic hydrocarbons having about the same configuration and molecular weight, they are often very difficult to treat to reduce their cold flow temperatures. The difficulty generally lies in the fact that the paraffinic compounds have low solubility in petroleum diesel and thus are susceptible to solidification/crystallization at low temperatures. As little as 2% paraffinic compounds can cause a conventional diesel fuel to completely solidify.

In petroleum diesel, it can be desirable to have a wide paraffin distribution. It is known in the art that it easier to treat a diesel fuel to improve cold flow properties with a broad paraffin distribution than a narrower distribution. It is also known that it is more difficult to treat a diesel fuel with a higher wax content as compared to one having a lower wax content. Finally, since hydrotreating eliminates most saturation, it serves to make paraffinic compounds more similar and actually creates paraffinic compounds by the saturation of aromatic compounds. So, in the case of petroleum diesel, it is often not desirable to hydrotreat the diesel.

Surprisingly, the algal derived HTRD useful with the present application are, in fact, treatable for cold flow using some of the same additives useful with petroleum diesel. Additives that may be used with the embodiments of the application include: ethylene vinyl acetate co-polymers, “terpolymers’ which are polymers of ethylene; vinyl acetate and a third monomer such as a vinyl carboxylate; polyalkyl methacrylates; alphaolefin maleic anhydride copolymers and ester or imide derivatives of alphaolefin maleic anhydride copolymers. Combinations of these compounds may also be used. These additives may have a molecular weight (Mw) of about 2,000 to 30,000 and most preferably between 3,000 and 5,000. The effective treat rates may be between 0.0025 vol-% and 5% vol-%.

Also surprising was that HTRD derived from animal fat was also treatable with some of the same additives useful with petroleum diesel.

The additives of the disclosure may be employed using an alkyl phenol resin synergist. The alkyl phenol resin may be prepared by reacting an alkyl phenol with an aldehyde. Aldehydes useful for preparing the alkyl phenol resins include formaldehyde, but higher aldehydes may also be used. Higher aldehydes which may be used to prepare the alkyl phenol resins include those aldehydes having from 2 to about 5 carbons.

The alkyl phenol resins may have a molecular weight (Mw) of from about two thousand to about twenty five thousand Daltons. In one embodiment, the alkyl phenol resin has a molecular weight of from about four to about twenty thousand. In still another embodiment, the alkyl phenol resin has a molecular weight of from about five to about ten thousand. While the structure of the alkyl phenol resins useful with the invention has been described as the reaction product of certain starting materials, the alkyl phenol resins may be prepared by any means known to those skilled in art to be useful for preparing such resins.

The biofuel of the disclosure may be 100% HTRD or an admixture of HTRD and petroleum diesel. The two components may be admixed in a ratio of from 2:98 to 98:2. In some embodiments the ratio of HTRD to Petroleum diesel is from 75:25 to 25:75. In other embodiments, this ratio is about 1:1.

The hydrotreated renewable diesel may be corrosive and require employment of an additive to mitigate corrosion. Additives useful from mitigating such corrosion may be any known to those of ordinary skill in the art, but include fatty acid oligomers, and in some embodiments dimers or trimers of such oligomers; blends of fatty acid oligomers; alkenyl or alkyl anhydrides, including but not limited to C₁₂ or C₁₆ anhydrides such as dodecenyl succinic anhydride (DDSA), tetrapropenyl succinic anhydride (TPSA) and hexadecenyl succinic anhydride (HDSA); amide, ester or amide/ester derivatives of succinic anhydrides; di-acids of succinic anhydrides; blends of succinic anhydrides, anhydride derivatives and/or fatty acids.

The biofuels, including both hydrotreated renewable diesels and combination of hydrotreated renewable diesels and petroleum diesels may require the use of an additive to increase their conductivity in order to abate static electrical charges. Any additive known to those of ordinary skill in the art may be used for such a purpose. Such additives may include combinations of compounds such as acrylates and sulfones. Specific compounds which may be useful with the method of the disclosure include but are not limited to polyacrylates, most preferably polymethacrylate; organosulfur compounds including sulfones, polysulfones and sulfates; acrylonitrile and copolymers of acrylonitrile such as alphaolefin acrylonitrile or styrene acrylonitrile; quaternary ammonium compounds; alkylphenol-aldehyde resins; oxyalkylated alkylphenol resins; and combinations therein.

EXAMPLES

The following examples are provided to illustrate the present invention. The examples are not intended to limit the scope of the present invention and they should not be so interpreted. Amounts are in weight parts or weight percentages unless otherwise indicated.

Example 1

Pour points were determined for a 50/50 admixture of a petroleum diesel and a HTRD, and then with petroleum diesel could flow additive. The admixture of petroleum diesel and HTRD are heated to at least 20° F. above their cloud point and then admixed with the additive and then the pour points are determined. The additive, BIOQUEST 9928, is a terpolymer. The 50/50 admixture of Petroleum Diesel:HTRD had a Pour Point of 10° F. When treated with 200 ppm and 400 ppm of BIOQUEST 9928, the flow point observed was 5° F.

Example 2

Pour points were determined for a 75:25 admixture of a petroleum diesel, a HTRD, and then with blends of same including an additive. The admixture of petroleum diesel and HTRD are heated to above their cloud point and then admixed with the additive and then the pour points are determined. The additive, BIOQUEST 9928, is a terpolymer. The 75:25 admixture of Petroleum Diesel:HTRD had a Pour Point of 0° F. When treated with 200 ppm of BIOQUEST 9928, the flow point observed was −10° F. When treated with 400 ppm of BIOQUEST 9928, the flow point observed was −40° F.

Example 3

Pour points were determined on a straight HTRD derived from beef tallow and then with blends of same including an additive. The HTRD was admixed with the additive at a temperature at least 20° F. above the cloud point of the HTRD and then the pour points are determined. The additive, BIOQUEST 9928, is a terpolymer. This 100% HTRD had a base pour point of +5° F. When treated with 2500 ppm BIOQUEST 9928, the flow point was lowered to below −45° F.

Dosage, Sample ID Additive ppm PP(° F.) HTRD — — 5; 5 HTRD BIO9928 500 5 HTRD BIO9928 1000 5 HTRD BIO9928 2000 5 HTRD BIO9928 2500 <−45 HTRD BIO9928 3000 <−45 

What is claimed is:
 1. A biofuel comprising hydrotreated renewable diesel, and at least one petroleum diesel cold flow improver additive.
 2. The biofuel of claim 1 wherein the at least one petroleum diesel cold flow improver additive is selected from the group consisting of: ethylene vinyl acetate co-polymers, terpolymers of ethylene; vinyl acetate and a third monomer; polyalkyl methacrylates; alphaolefin maleic anhydride copolymers and ester or imide derivatives of alphaolefin maleic anhydride copolymers and combinations thereof.
 3. The biofuel of claim 2 wherein the additive is an ethylene vinyl acetate co-polymer.
 4. The biofuel of claim 2 wherein the additive is a terpolymer of ethylene; vinyl acetate and a third monomer.
 5. The biofuel of claim 4 wherein the third monomer is vinyl carboxylate.
 6. The biofuel of claim 2 wherein the additive is a polyalkyl methacrylate.
 7. The biofuel of claim 2 wherein the additive is a combination of at least two members selected from the group consisting of: ethylene vinyl acetate co-polymers, terpolymers of ethylene; vinyl acetate and a third monomer; polyalkyl methacrylates; and combinations thereof.
 8. The biofuel of claim 1 wherein the one petroleum diesel cold flow improver additive has a molecular weight (Mw) of from about 2,000 to about 30,000.
 9. The biofuel of claim 8 wherein the additive has a molecular weight (Mw) of from about 3,000 to about 5,000.
 10. The biofuel of claim 1 wherein the effective treat rate is from about 0.0025 vol-% to about 5% vol-%.
 11. The biofuel of claim 1 further comprising a petroleum diesel.
 12. The biofuel of claim 1 further comprising a synergist.
 13. The biofuel of claim 12 wherein the synergist is an alkyl phenol resin.
 14. The biofuel of claim 13 wherein the alkyl phenol resin is prepared from a formulation comprising an aldehyde having from about 2 to about 5 carbons.
 15. The biofuel of claim 13 wherein the alkyl phenol resin is prepared from a formulation comprising formaldehyde.
 16. The biofuel of claim 13 wherein the alkyl phenol resin has a molecular weight (Mw) of from about two thousand to about twenty five thousand Daltons.
 17. The biofuel of claim 16 wherein the alkyl phenol resin has a molecular weight (Mw) of from about five to about ten thousand.
 18. The biofuel of claim 11 wherein the ratio of hydrotreated renewable diesel to Petroleum diesel is from 75:25 to 25:75.
 19. The biofuel of claim 11 wherein the ratio of hydrotreated renewable diesel to Petroleum diesel is about 1:1.
 20. The biofuel of claim 1 wherein the hydrotreated renewable diesel is derived from algae.
 21. A method of preparing a biofuel comprising an admixture of petroleum diesel, hydrotreated renewable diesel, and at least one petroleum diesel cold flow improver wherein the at least one petroleum diesel cold flow improver is introduced into an admixture of petroleum diesel, hydrotreated renewable diesel at a temperature above the cloud point of the admixture of petroleum diesel, hydrotreated renewable diesel. 